Acoustic transducers



Sept- 11, 1962 R. B. BLIZARD 3,053,338

ACOUSTIC TRANSDUCERS Filed Oct 30, 1959 4/ Robert .5. .B/IZCIIQINVENTOR.

ATI'UR/VEF United States Patent 3,053,338 ACOUSTIC TRANSDUCERS Robert B.Blizard, Houston, Tex., assignor to Schlumberger Well SurveyingCorporation, Houston, Tex a corporation of Texas Filed Oct. 30, 1959,Ser. No. 849,891 6 Claims. (Cl. 181-.5)

This invention relates to acoustic transducers and more particularlymechanical acoustic transducers for generating' acoustic energy in awell bore containing fluid.

It is an object of the present invention to provide new and improvedmechanical transducer apparatus for developing acoustic energy in a wellbore.

A mechanical acoustic transducer for borehole use as contemplated by thepresent invention includes a housing adapted for passage through aborehole and having a resiliently mounted, reciprocating piston memberwhich acts upon the fluid in the well to develop pressure waves. Theresilient mounting is such that high differential pressures on eitherside of the piston may be sustained. to permit the interior of thehousing to be at atmospheric pressure so that movement of an inertiamember in the housing to actuate the piston is not retarded.

The novel features of the present invention are set forth withparticularity in the appended claims. The present invention, both as toits organization and manner of operation together with further objectsand advantages thereof, may best be understood by way of illustrationand example of certain embodiments when taken in conjunction with theaccompanying drawings in which:

FIG. 1 shows a portion of a borehole apparatus in section embodying thepresent invention disposed in the borehole; and

FIG. 2 shows another embodiment of the present invention in section.

Referring now to FIG. 1, a suitable fluid-tight housing or support 10(only a portion being shown) is adapted. to be transported through abore 11 by means of a cable (not shown) and a winch (not shown) locatedat the surface of the earth in a customary manner. The bore 11 whichtraverses the earth formations contains the customary drilling fluid 13which provides a medium for transmission of acoustic energy between theapparatus and the earth formations.

Housing 10 is generally tubular in shape and has a lower cylindrical endsection 14. End section 14 is suitably hollowed out to receive a disccam 15 mounted for rotation in the end section 14 and a hammer orinertia member 16 which is secured to one arm 17 of a bell crank 18. Thebell crank 18 is pivotally mounted to the end section 14 and has anotherarm 19 which is in a contacting relationship to the cam 15 so as tofunction as a cam follower. A spring member 20 is also suitably securedto the end section 14 and has a portion thereof in contactingrelationship with the crank arm 19 to resiliently bias the arm'intocontact with the cam 15. The layout of cam 15 provides a surface 21which lies in a plane A passing through the central axis of the disc andextending between adjacent portions 22, 23 of the cam having differentradii. The circumference of the cam 15 is defined by radii of increasinglength starting from the smallest radius portion 22 adjacent surface 21and going clockwise about the cam to the largest radius portion 23adjacent to the surface 21.

Thus, when the cam 15 is rotated by a motor (not shown) in acounterclockwise manner, for example, a uniform angular displacement ina clockwise direction is imparted to the follower crank arm 19 whichmoves the hammer member- 16 along an arc until the follower crank armrides past the largest radius portion 23 and surface 3,053,338 PatentedSept. 11, 1962 v 2 21 whereupon the hammer 16 is freeto drop. The

hammer 16 is provided with sufficient mass so that its momentum may beemployed to impart mechanical energy to a piston member 33 to produce apressure wave in the fluid. The interior of the housing end section 14is preferably gas-filled at atmospheric pressure so that the movement ofthe hammer member is not impeded or retarded.

The outer, lower extremity of the housing end section 14 has a flatsurface 25 which lies in a plane perpendicular to the sheet of drawingand at a preferred angle of 1130" relative to a vertical central axisthrough the end section 14. An opening extends between the interior wall30 of the housing and flat surface 25 and has a central axis 26 which istransverse with respect to the vertical axis of the housing. Portions ofthe housing end section about the opening define first and second tionin a plane in which the axis 26 lies, the base or chord of thesemicircular configuration lying on an imaginary conical surface aboutthe axis 26 which would intersect the adjacent circular edges 31 and 32between adjacent surfaces 28, 29 and 29, 27, respectively.

A piston member 33 having first and second cylindrical portions 34 and35 of different diameters is adapted to be slidably received by thefirst and second cylindrical surfaces 27 and 28 and has an intermediatethird portion 36 having a conical configuration and joining the firstportion to the second portion. In the normal position of the pistonmember 33 the conical configuration will intersect the interconnection32 between surfaces 27, 29 and the conical angle of the conicalconfiguration is less than the conical angle of the imaginary conicalsurface thereby to form a geometrical configuration. The geometricalconfiguration is bounded by the semicylindrical annular surface 2901:the housing and by a part of the second cylindrical portion 35 and thethird portion 36 of the piston member 33. The cylindrical portion 35 ofpiston 24 also extends inwardly into the interior of the housing so asto be struck by the hammer member 16 when the hammer member is droppedwhile the forward surface 38 of the piston 24 generally does not extendbeyond the fiat surface 25. The forward surface 38 is shown with aconcavity which permits a substantially planar wave to be generated.

Within the geometrical configuration or volume defined by annularsurface 29, the part of second cylindrical portion 37 and third portion36 of piston member 33 is material 39 having a relatively highcompressibility such as elastomers, for example, the material entirelyfilling the geometrical configuration. It will be noted that portions ofthe material in the volume have a greater diameter than the cylindricalportion 34 of the piston member 33 so that inward movement of the pistonmember applies a radial compressive force as well as an axialcompressive force. Also, a relatively large contact area on the thirdportion of the piston member is provided to reduce the not be displacedinwardly to a point where the material does not resiliently support themember.

From the foregoing it will be appreciated that the transducer translatessound through a pressure resistant hOusing by means of a piston having asmaller area opening into the interior of the housing and a larger areaopening to the exterior of the housing. The opening in the housing whichreceives the piston has an intermediate volume between the smaller andlarger areas filled with material of relatively high compressibilitywhich effectively pressure seals the piston in the housing yet permitsthe transmission of sound.

The inclination of the flat surface 25 at 11 30' from the vertical axisalso inclines the central axis 26 of the piston member 33 at 11 30" froma horizontal axis. Thus, for very high-speed formations, i.e., about25,000 feet per second the SOILJ energy is directed at the formations atthe preferred critical angle which permits the most effectivetransmission of sound through the formations.

Referring now to FIG. 2 where corresponding elements to those of FIG. 1are similarly identified, the material 39 is disposed adjacent thecylindrical surfaces 27 and 28 and has an annular groove 40 opening tosurface 29 which receives a relatively incompressible fluid 41 such assilicone oil which may be introduced to the groove via an opening 42.

While the above forms of the invention preferably entail bonding of thematerial in the volume between the piston member and housing, it shouldbe appreciated that other techniques to fluid seal the piston memberwith respect to the housing may be effected within the practice of thepresent invention.

While particular embodiments of the present invention have been shownand described, it is apparent that changes and modifications may be madewithout departing from this invention in its broader aspects, andtherefore the aim in the appended claims is to cover all such changesand modifications as fall within the true spirit and scope of thisinvention.

What is claimed is:

1. An acoustic transducer system comprising: a pressure-resistant hollowhousing having a first longitudinallyextending axis, said housing havingan opening extending between its interior and exterior walls about asecond axis'which is transverse with respect to said first axis,portions of said housing about said opening defining first and secondcylindrical surfaces about said second axis having different diametersand opening respectively to the exterior and interior walls of thehousing and terminating short of one another within the housing wall,the diameter of said first surface being greater than the diameter ofsaid second section, said housing portions further defining anintermediate, third, annular surface interconnecting said first andsecond surfaces, a piston member having first and second cylindricalportions of different diameters adapted to be slidably received by saidfirst and second cylindrical surfaces and an intermediate third portionjoining said first portion to said second portion, said third annularsurface of said housing and a part of said second cylindrical portionand said third portion of said piston member defining a volumetherebetween, material having a relatively high compressibility fillingsaid volume, and means in said housing for imparting mechanical energyto said piston member whereby a pressure wave may be produced in a wellbore containing liquid.

2. An acoustic transducer system comprising: a pressure resistant hollowhousing having a first longitudinallyextending axis, said housing havingan opening extending between its interior and exterior walls about asecond axis which is transverse with respect to said first axis,portions of said housing about said opening defining first and secondcylindrical surfaces about said second axis exterior and interior wallsof the housing and terminating short of one another within the housingwall, the diameter of said first surface being greater than the diameterof said second section, said housing portions further defining anintermediate, third, annular surface interconnecting said first andsecond surfaces, a piston member having first and second cylindricalportions of different diameters adapted to be slidably received by saidfirst and second cylindrical surfaces and an intermediate third portionjoining said first portion to said second portion, said third annularsurface of said housing and a part of said second cylindrical portionand said third portion of said piston member defining a volumetherebetween, material having a relatively high compressibility fillingsaid volume, said material including elastic sealing portions disposedat each of said first and second cylindrical surfaces, and means in saidhousing for imparting mechanical energy to said piston member whereby apressure wave may be produced in a well bore containing liquid.

3. An acoustic transducer system comprising: a fluidtight hollow housinghaving a first longitudinally-extending axis, said housing having anopening extending between its interior and exterior walls about a secondaxis which is transverse with respect to said first axis, portions ofsaid housing about said opening defining first and second cylindricalsurfaces about said second axis having different diameters and openingrespectively to the exterior and interior walls of the housing andterminating short of one another within the housing wall, the diameterof said first surface being greater than the diameter of said secondsurface, said housing portions further defining an intermediate, third,annular surface interconnecting said first and second surfaces, saidthird surface having a curvilinear cross-sectional configuration whentaken along a plane in which said second axis lies having a linear baselying on a first imaginary conical surface about said second axis whichintersects the interconnections between adjacent surfaces and havingportions of greater diameter than said diameter of said first surface, apiston member having first and second cylindrical portions of differentdiameters adapted to be slidably received by said first and secondcylindrical surfaces and an intermediate third portion joining saidfirst portion to said second porton, the junctions of said first andthird portions lying on a second imaginary conical surface about saidsecond axis, the conical angle of said second imaginary conical surfacebeing less than the conical angle of said first imaginary conicalsurface thereby to form a geometrical configuration bounded by saidcurvilinear surface of said housing and by a portion of said secondcylindrical portion and by said third portion of said piston member, anannular resilient member secured to said surfaces forming saidgeometrical configuration, and means in said housing for impartingmechanical energy to said piston member whereby a pressure wave may beproduced in a well bore containing liquid.

4. An acoustic transducer system comprising: a fluidtight hollow housinghaving a first longitudinally-extending axis, said housing having anopening extending between its interior and exterior walls about a secondaxis which is trnasverse with respect to said first axis, portions ofsaid housing about said opening defining first and second cylindricalsurfaces about said second axis having different diameters and openingrespectively to the exterior and interior walls of the housing andterminating short of one another within the housing wall, the diameterof said first surface being greater than the diameter of said secondsurface, said housing portions further defining an intermediate, third,annular surface interconnecting said first and second surfaces, saidthird surface having a curvilinear cross-sectional configuration whentaken along a plane in which said second axis lies having a linear baselying on a first imaginary conical surface about said second axis whichintersects the interhaving different diameters and opening respectivelyto the connections between adjacent surfaces and having portions ofgreater diameter than said diameter of said first surface, a pistonmember having first and second cylindrical portions of differentdiameters adapted to be slidably received by said first and secondcylindrical surfaces and an intermediate third portion joining saidfirst portion to said second portion, the junctions of said first andthird portions and said second and third portions lying on a secondimaginary conical surface about said second axis, the conical angle ofsaid second imaginary conical surface being less than the conical angleof said first imaginary conical surface thereby to form a geometricalconfiguration bounded by said curvilinear surface of said housing and bya portion of said second cylindrical portion and by said third portionof said piston member, an annular resilient member secured to saidsurfaces forming said geometrical configuration, said member having anannular recess opening to said curvilinear surface, a relativelyincompressible fluid received in said annular recess, and means in saidhousing for imparting mechanical energy to sad piston member whereby apressure wave may be produced in a well bore containing liquid.

5. An acoustic transducer system comprising: a fluidtight hollow housinghaving a first longitudinally-extending axis, said housing having anopening extending between its interior and exterior walls about a secondaxis which is transverse with respect to said first axis, portions ofsaid housing about said'opening defining first and second cylindricalsurfaces about said second axis having different diameters and openingrespectively to the exterior and interior walls of the housing andterminating short of one another within the housing wall, the diameterof said first surface being greater than the diameter of sad secondsurface, said housing portions further defining an intermediate andthird, annular surface interconnecting said first and second surfaces,said third surface having a curvilinear cross-sectional configurationwhen taken along. a plane in which said second axis lies having a linearbase lying on an imaginary conical surface about said second axis whichintersects the interconnection between adjacent surfaces and havingportions of greater diameter than said diameter of said first surface, apiston member having first and second cylindrical portions of differentdiameters adapted to be slidably received by said first and secondcylindrical surfaces and an intermediate third portion having agenerally conical configurationand joining said first portion to saidsecond portion, the conical angle of said conical configuration beingless than the conical angle of said imaginary conical surface thereby toform a geometrical configuration bounded by said curvilinear surface ofsaid housing and by a portion of said second cylindrical portion and bysaid third portion of said piston member, an annular resilient membersecured to said surfaces forming said geometrical configuration, andmeans in said housing for imparting mechanical energy to said pistonmember whereby a pressure wave may be produced in a well bore containingliquid.

6. An acoustic transducer system comprising: a fluidtight hollow housinghaving a first longitudinally-extending axis, said housing having anopening extending between its interior and exterior walls about a secondaxis which is transverse with respect to said first axis, portions ofsaid housing about said opening defining first and second cylindricalsurfaces about said second axis having difierent diameters and openingrespectively to the exterior and interior walls of the housing andterminating short of one another within the housing wall, the diameterof said first surface being greater than the diameter of said secondsurface, said housing portions further defining an intermediate andthird, annular surface interconnecting said first and second surfaces,said third surface having a somewhat semicircular cross-sectionalconfiguration when taken along a plane in which said second axis lies,the base of said semicylindrical configuration lying on an imaginaryconical surface about said second axis which intersects theinterconnection between adjacent surfaces, a piston member having firstand secondcylindrical portions of different diameters adapted to beslidably received by said first and second cylindrical surfaces and anintermediate third portion having a conical configuration and joiningsaid first portion to said second portion, the conical angle of saidconical configuration being less than the conical angle of saidimaginary conical surface thereby to form a geometrical configurationbounded by said semicylindrical surface of said housing and by a portionof said second cylindrical portion and by said third portion of saidpiston member, an annular resilient member bonded to said surfacesforming said geometrical configuration, and means in said housing forimparting mechanical energy to said piston member wereby a pressure wavemay be produced in a well bore containing liquid.

References Cited in the file of this patent UNITED STATES PATENTS HarrisAug. 2, 1960

